1. Field of the Invention
The present invention relates to a cartridge accommodating therein an information carrier medium which may be a length of magnetic recording tape, a magnetic recording disc, an optical disc or a magneto-optical disc.
2. Description of the Prior Art
The cartridge for accommodating the information carrier medium is currently available in various types. Of those types, the present invention pertains to a single-reel tape cartridge generally used in association with a computer for data back-up purposes, a compact two-reel tape cartridge generally known as a DAT (digital audio tape) cartridge, and a disc cartridge. In any event, the present invention is applicable to any type of cartridge having a spring-biased slide shutter.
As is well known to those skilled in the art, the single-reel tape cartridge comprises a generally rectangular box-like housing having top and bottom panels and a peripheral wall Including front, rear and side walls and joining the top and bottom panels together with a tape chamber defined therein. The front wall has an access opening defined therein, through which a length of magnetic recording tape wound around a single reel within the tape chamber is selectively drawn outwardly and retracted into the housing. The access opening is normally closed by a shutter carried by the housing.
In this single-reel tape cartridge, the Japanese Laid-open Patent Publication No. 8-43940 discloses the shutter that is pivotally supported and is normally biased by a single-coiled torsional spring towards a closed position in which the access opening is closed. Although any possible ingress of dusts into the tape chamber is effectively and advantageously avoided, the pivotally supported shutter poses a problem in that when the shutter is opened against the biasing force of the torsional spring, the shutter protrudes a considerable distance outwardly of the housing, particularly outwardly from the front wall of the housing. Considering that opening of the shutter is mainly required when the tape cartridge is loaded in a tape drive, the freedom of disposition of a tape loading mechanism and a tape transport mechanism in the tape drive is limited and a relatively large space has to be secured within the tape drive to accommodate the shutter then in the opened position. This not only restricts the freedom of design, but also hampers downsizing and simplification of the tape drive and increase of the tape transport speed.
In an attempt to simplify the structure of and improve the function of the tape drive, the inventors of the present invention have examined the possible use of a slide shutter supported for sliding motion between opened and closed positions along the front wall of the cartridge housing. In principle, the slide shutter can make use of a support structure similar to that used in connection with a protect notch that is used in the standard tape cartridge for avoiding an inadvertent erasure of information recorded on the length of magnetic tape.
However, in the case of the single-reel tape cartridge, a free end of the length of magnetic tape wound around the single reel has to be retained at a predetermined location inwardly of the housing and adjacent the access opening together with a retainer pin around which the free end of the magnetic tape is secured. Accordingly, when the slide shutter is applied to the single-reel tape cartridge, the access opening must have a substantial width as measured in a direction along the front wall of the housing so that a tape loading element in the tape drive which serves to draw the magnetic tape outwardly or allow the magnetic tape to be withdrawn into the housing can move without being interfered by any other obstruction. This correspondingly results in the necessity of the slide shutter to t:ravel an increased stroke between the closed and opened positions.
When it comes to the slide shutter required to travel a substantial distance between the closed and opened positions, difficulties would be often encountered in choosing the biasing member for biasing the slide shutter normally towards the closed position and, also, optimizing the biasing force of such biasing member regardless of the position thereof between the closed and opened positions. Specifically, if the stroke of movement of the slide shutter between the closed and opened positions is of a small distance, the use of the standard single-coiled torsional spring would work sufficiently, provided that the wire forming the torsional spring and/or the number of turns of the single coil in the torsional spring are properly chosen and adjusted.
However, if such torsional spring is used in association with the increased stroke of movement of the slide shutter, the single-coiled torsional spring of a given size would exerts an insufficient biasing force with the spring arms expanding in respective directions away from each other. In other words, for a given size and design of the single-coiled torsional spring, the use thereof in association with the slide shutter is limited where a substantially equal quantity of the biasing force is desired or required regardless of the position of the slide shutter.
In addition, where the single-coiled torsional spring is used in the single-reel tape cartridge in an erected fashion with the spring arms extending in a plane parallel to the plane of the access opening or the front wall of the cartridge housing of a size so standardized that the cartridge can be compatible with any of the existing tape drives of different makes, the spring arms must have a limited length that is smaller than, for example, the thickness of the cartridge. Accordingly, the use of the slide shutter in the single-reel tape cartridge would pose a problem in that the distance of expansion of the spring arms in the respective opposite direction would be unable to cover the entire stroke of movement of the slide shutter.
Another problem associated with the increased stroke of movement of the slide shutter lies in that since the spring arms must be of a type capable of resiliently displacing or expanding a correspondingly increased distance relative to each other in the respective directions opposite to each other, the single-reel tape cartridge would exert the considerably varying biasing force. For this reason, even though the single-coiled torsional spring could successfully used in the single-reel tape cartridge, it is apparent that the biasing force exerted on the slide shutter in the closed position and that on the slide shutter in the opened position give rise to a considerable difference, and therefore the single-coiled torsional spring tends to be deteriorate when used for a prolonged period of time.
The extent of change of the biasing force exerted by the single-coiled torsional spring may be reduced if the number of turns forming the single coil in the torsional spring is increased. However, the increased number of the turns of the coil results in a corresponding increase of the axial length of the coil, requiring a relatively large space for installation in the cartridge housing, which in turn results in increase of the size of the cartridge housing.
In any event, the use of either the compression spring or the tension spring, even though having a small diameter, does not contribute to reduction in space required for installation thereof and, hence, the size of the cartridge housing.